Research project: Lubricant nanoadditives
Tungsten disulphide (WS2) nanoparticles have excellent tribological properties and are a potential replacement for current problematic additives.
Project Overview
WS 2 nanoparticles possess remarkable tribological and physicochemical properties which recommend them as potential candidates for replacing problematic additives still in use in lubricants. This project has shown that the mechanism of action of WS 2 NPs in high-temperature, high-pressure contacts is based on the generation of a thick chemical tribofilm on the steel wear tracks (200 nm) (shown in Figure 1). The specific properties of the WS 2 tribofilms are responsible for reduced friction and wear during tribological tests. The layered structure of the film is shown in Figure 2.
The friction, wear and micromechanical properties of WS 2 tribofilms are compared with those of tribofilms formed by the zinc dialkyldithiophosphate (ZDDP) antiwear additive and ZDDP-organic friction modifier (OFM) mixture (Figure 3). Nanoindentation measurements showed that WS 2 generates tribofilms with higher values of hardness and Young’s modulus than ZDDP and ZDDP+OFM, which explains its excellent antiwear properties. The friction performance of WS 2 surpassed that of ZDDP+OFM. The striking reduction of boundary friction is credited to the layered structure of the WS 2 tribofilm, with exfoliated/squashed WS 2 nanoparticles that fill the gaps and cover the reacted tribofilm.
